The present invention relates to boiler controls and more particularly to multiple sequential valve controls especially useful in boiler controls in combined cycle or other electric power plants.
Multiple valves may be employed to control a single boiler feedwater or other process flow in order to obtain relatively resolution control over a wide flow range. Typically, a M/A station is provided for placing the flow under either automatic process flow control or manual flow control. Provision normally is then needed for executing bumpless process transfers from manual to automatic modes of operation.
Although bumpless M/A transfer operations are generally well known in process control technologies, the known techniques generally are limited to applications where a M/A station is associated with each valve. Efficient systems have not been developed for cases in which a single M/A station is economically tied to multiple valves controlling a single flow in boiler or other processes.